<
https://theconversation.com/flooding-rains-ocean-gains-how-a-huge-murray-flood-gave-the-sea-a-feast-284567>
"For decades, the rivers of the Murray-Darling Basin have been heavily
regulated by dams and irrigation networks. As a result, the volume of water
entering the ocean is about 60% smaller than 100 years ago. But nature broke
through during massive floods over the summer of 2022–23, when heavy rains
filled the Basin’s waterways.
The threshold for a flood on the Murray is when the daily water flow at the
Victoria-South Australian border reaches 50 gigalitres a day. This flood
reached 168 gigalitres a day – the largest in 66 years. A colossal plume of
muddy floodwater reached 40 kilometres out from the Murray mouth into the
Southern Indian Ocean.
For marine creatures, this was a dramatic event. What did it do to their
ecosystems? To find out, we compared marine animals living directly inside the
flood plume with those living further away in normal saltwater.
Our new research found the flood delivered a burst of nutrients into the ocean.
We estimate more than 200,000 tonnes of organic carbon were carried out to sea
between July 2022 to June 2023 – 29 times more than the same period in 2020–21.
This organic carbon came from the Basin’s rivers and their floodplains, and
included large numbers of common carp. Millions of juvenile carp — a highly
destructive, invasive freshwater fish — were flushed into the open sea.
Because carp cannot survive in saltwater, they perished en masse. Dead carp
piled up on local beaches at astonishing densities of up to 7 kilograms per
square metre. In marine rock pools more than 20km from the river mouth, we saw
the local crab species such as the purple mottled shore crab and the reef crab
having a field day."
Cheers,
*** Xanni ***
--
mailto:xanni@xanadu.net Andrew Pam
http://xanadu.com.au/ Chief Scientist, Xanadu
https://glasswings.com.au/ Partner, Glass Wings
https://sericyb.com.au/ Manager, Serious Cybernetics
